/*
- Glaurung, a UCI chess playing engine.
- Copyright (C) 2004-2008 Tord Romstad
+ Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+ Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
- Glaurung is free software: you can redistribute it and/or modify
+ Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
-
- Glaurung is distributed in the hope that it will be useful,
+
+ Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
-
+
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-#if !defined(TT_H_INCLUDED)
+#ifndef TT_H_INCLUDED
#define TT_H_INCLUDED
-////
-//// Includes
-////
-
-#include "depth.h"
-#include "position.h"
-#include "value.h"
-
-
-////
-//// Types
-////
-
-/// The TTEntry class is the class of transposition table entries.
-
-class TTEntry {
-
-public:
- TTEntry();
- TTEntry(Key k, Value v, ValueType t, Depth d, Move m, int generation);
- Key key() const;
- Depth depth() const;
- Move move() const;
- Value value() const;
- ValueType type() const;
- int generation() const;
-
-private:
- Key key_;
- uint32_t data;
- int16_t value_;
- int16_t depth_;
+#include <cstddef>
+#include <cstdint>
+
+#include "misc.h"
+#include "types.h"
+
+namespace Stockfish {
+
+// TTEntry struct is the 10 bytes transposition table entry, defined as below:
+//
+// key 16 bit
+// depth 8 bit
+// generation 5 bit
+// pv node 1 bit
+// bound type 2 bit
+// move 16 bit
+// value 16 bit
+// eval value 16 bit
+
+struct TTEntry {
+
+ Move move() const { return Move(move16); }
+ Value value() const { return Value(value16); }
+ Value eval() const { return Value(eval16); }
+ Depth depth() const { return Depth(depth8 + DEPTH_OFFSET); }
+ bool is_pv() const { return bool(genBound8 & 0x4); }
+ Bound bound() const { return Bound(genBound8 & 0x3); }
+ void save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev);
+
+ private:
+ friend class TranspositionTable;
+
+ uint16_t key16;
+ uint8_t depth8;
+ uint8_t genBound8;
+ uint16_t move16;
+ int16_t value16;
+ int16_t eval16;
};
-/// The transposition table class. This is basically just a huge array
-/// containing TTEntry objects, and a few methods for writing new entries
-/// and reading new ones.
+// A TranspositionTable is an array of Cluster, of size clusterCount. Each
+// cluster consists of ClusterSize number of TTEntry. Each non-empty TTEntry
+// contains information on exactly one position. The size of a Cluster should
+// divide the size of a cache line for best performance, as the cacheline is
+// prefetched when possible.
class TranspositionTable {
-public:
- TranspositionTable(unsigned mbSize);
- ~TranspositionTable();
- void set_size(unsigned mbSize);
- void clear();
- void store(const Position &pos, Value v, Depth d, Move m, ValueType type);
- bool retrieve(const Position &pos, Value *value, Depth *d, Move *move,
- ValueType *type) const;
- void new_search();
- void insert_pv(const Position &pos, Move pv[]);
- int full();
-
-private:
- unsigned size;
- int writes;
- TTEntry* entries;
- uint8_t generation;
+ static constexpr int ClusterSize = 3;
+
+ struct Cluster {
+ TTEntry entry[ClusterSize];
+ char padding[2]; // Pad to 32 bytes
+ };
+
+ static_assert(sizeof(Cluster) == 32, "Unexpected Cluster size");
+
+ // Constants used to refresh the hash table periodically
+ static constexpr unsigned GENERATION_BITS = 3; // nb of bits reserved for other things
+ static constexpr int GENERATION_DELTA =
+ (1 << GENERATION_BITS); // increment for generation field
+ static constexpr int GENERATION_CYCLE = 255 + (1 << GENERATION_BITS); // cycle length
+ static constexpr int GENERATION_MASK =
+ (0xFF << GENERATION_BITS) & 0xFF; // mask to pull out generation number
+
+ public:
+ ~TranspositionTable() { aligned_large_pages_free(table); }
+ void new_search() { generation8 += GENERATION_DELTA; } // Lower bits are used for other things
+ TTEntry* probe(const Key key, bool& found) const;
+ int hashfull() const;
+ void resize(size_t mbSize);
+ void clear();
+
+ TTEntry* first_entry(const Key key) const {
+ return &table[mul_hi64(key, clusterCount)].entry[0];
+ }
+
+ private:
+ friend struct TTEntry;
+
+ size_t clusterCount;
+ Cluster* table;
+ uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
};
+extern TranspositionTable TT;
-////
-//// Constants and variables
-////
-
-// Default transposition table size, in megabytes:
-const int TTDefaultSize = 32;
-
+} // namespace Stockfish
-#endif // !defined(TT_H_INCLUDED)
+#endif // #ifndef TT_H_INCLUDED
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